Instrumentation for label-free high throughput screening is commercially available today and is often used for detecting biomolecular interactions while testing new drugs. The typical label-free interrogation system employs microplates with wells which have biosensors incorporated therein that enable the detection of biomolecular interactions like material bindings, adsorptions etc. . . by monitoring changes in the refractive index at or near the sensing surfaces of the biosensors. For example, each biosensor has a sensing surface on which a ligand can be immobilized so that when an analyte which is in a solution located above the sensing surface interacts with the immobilized ligand then there would be a change in the refractive index. The label-free interrogation system interrogates each biosensor and detects this change in the refractive index and as a result is able to detect/monitor the biomolecular interaction between the immobilized ligand and the analyte which is useful while testing new drugs.
The typical microplate includes an open array of wells which are aligned with an array of biosensors that are located on the surface of a substrate which forms the bottoms of the wells. These open-air microplates perform well in most applications but there are some applications which require the use of flow-through assays (kinetic assays of association and dissociation) where a micro-fluidic microplate would be preferable to use instead of the open-air microplate. Unfortunately, the existing micro-fluidic microplates, suffer from a problem of maintaining a closed system so one or more fluids can be transferred from a fluid delivery system into the micro-fluidic microplate where they flow over the biosensors and are then removed from the micro-fluidic microplate without being exposed to the air and/or being spilled on top of the micro-fluidic microplate. In other words, there is often a leakage/sealing problem that occurs at the interface between these micro-fluidic microplates and the fluid delivery system.
To address this sealing/leakage problem, the assignee of the present invention has developed several different closed flow-through microplates which were disclosed and discussed in U.S. patent application Ser. No. 10/155,540 filed May 24, 2002 and entitled “Microcolumn-Based, High-Throughput Microfluidic Device” (the contents of this document are incorporated by reference herein). Although these closed flow-through microplates work well when performing a flow-through assay there is still a desire to improve upon and enhance the existing closed flow-through microplates. This particular need and other needs have been satisfied by the present invention